Microbes, rain, and climate

From the American Chemical Society

Dust — and the microbes hitching rides on it — influences rain, climate

SAN FRANCISCO, Aug. 13, 2014 — Dusty air blowing across the Pacific from Asia and Africa plays a critical role in precipitation patterns throughout the drought-stricken western U.S. Today, a scientist will present new research suggesting that the exact chemical make-up of that dust, including microbes found in it, is the key to how much rain and snow falls from clouds throughout the region. This information could help better predict rain events, as well as explain how air pollution from a variety of sources influences regional climate in general.

She will present a talk on how aerosols impact clouds and climate at the 248th National Meeting & Exposition of the American Chemical Society (ACS), the world’s largest scientific society. The meeting is taking place here through Thursday and features nearly 12,000 scientific presentations.

“We’ve learned that not all of the particles in the air at high altitudes have the same influence on clouds. We’re starting to think that these differences contribute to how rain gets distributed,” says Kim Prather, Ph.D.

Most of the dust that Prather’s team at the University of California, San Diego, detects in clouds and precipitation originates in Asian and Chinese deserts. It gets swept westward by the jet stream where it mixes with a variety of other airborne particles such as sea spray and smoke. Prather says that each of these types of particles — collectively known as aerosols — has its own, distinctive impact on clouds.

A major key to what turns ordinary clouds into rainmakers in the first place is their ability to form ice crystals around the microscopic particles that invade and “seed” them, Prather said. Without ice crystals as a catalyst, rain development inside clouds can be impaired.

“The standard belief is the more ice you have in a cloud, the more likely you will get precipitation out of it,” she says. “Our goal is to catch the first stages of ice forming and find out what exactly the chemical constituents are that the ice is forming on.”

Prather and her team use special single-particle mass spectrometers, which sample cloud droplets and ice crystals in real-time. The instruments are used aboard research aircraft flying through clouds high above the western seaboard. One of her most recent — and surprising — discoveries is that the material she measures is remarkably loaded with signs of life.

“We’re seeing lots of biological components such as bacteria and molecules associated with microbial life,” she says. “In fact, many of the species we find in the ice crystals have these biological chemicals and are not simply dust particles.”

Prather speculates that the microbes hitch a ride on bits of sand, iron and other debris swept aloft from desert regions. Microbes and biological components could also become mixed with the dust as it is transported across the Pacific. She and her team are eager to learn just how important these bioparticles are in the rainmaking process.

Such research eventually could lead to more accurate weather forecasting and rainfall predictions, she believes. Only recently have some computer weather models begun to use dust data gathered by satellite imagery that captures dust’s sweep toward the west coast.

“Long term, our goal is to be able to predict how much precipitation we can expect to form when certain aerosols such as dust are coming toward us,” says Prather. “That’s a lofty goal but we’re making headway.”

Another pay-off to her research also could be a way to improve cloud-seeding technology. Since the late 1940s, cloud seeding in certain parts of the continental U.S. has been commonplace, even though results continue to be spotty. Prather says her current research may help identify better ways of seeding clouds based on the natural processes she studies. “It’s clear that Mother Nature has developed very effective ways to seed clouds, so perhaps we could take some tips from her.”


Prather acknowledges funding from the Centers for Chemical Innovation program at the National Science Foundation and the California Energy Commission.

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August 14, 2014 4:18 am

“Another pay-off to her research also could be a way to improve cloud-seeding technology.”
The problem with cloud seeding is that if it works reliably, then 20, 50, 100 miles downwind where the rain would have naturally fallen won’t get that rain. If cloud seeding becomes reliable I can envision the same kind of legal battles over the moisture in clouds that now occurs with irrigation water in rivers and lakes.

August 14, 2014 4:51 am

Microbes are being swept into the skies to their death? Save the microbes!

August 14, 2014 4:53 am

ddpalmer, certainly if the goal of cloud seeding is to extract water from the clouds.
Where I am they primarily seed (or maybe past tense, who knows these days?) clouds that are likely to form dangerous storms, especially with large hail. It is (was?) not unusual whenever I saw a large, angry black cloud roaring into town, to see the same nozzle equipped airplane ducking in and out of it.
Of course, the problem with that is the opposite: ANY human interaction is going to annoy someone, and as I recall people were suing whenever there was too much rain, because “the cloud seeding must have done it”.
On this part of the prairies it’s not unusual to have several huge, devastating hail storms roll past us per year. We hope they miss us, but as the population here booms there are an increasing number of people in their paths. Not surprisingly, they all scream “climate change” because they don’t remember these storms before…

Frank Kotler
August 14, 2014 4:56 am

“It gets swept westward by the jet stream where it mixes with a variety of other airborne particles such as sea spray and smoke. ”

Leo Morgan
August 14, 2014 5:06 am

It seems obvious that a warmer world with more CO2 would produce more microbes in the cloud/atmosphere ecosystem, and thus more rain. This would function as a negative feedback to AGW. However, obvious is not the same as right. My belief that this increased microbial seeding was likely was one of the reasons I am sceptical of Al ‘the North Pole will melt by 2010’ Gore’s environmental litany. However, after reading a report that claimed that bacteria seed only one raindrop in ten thousand, I abandoned that idea as grounds for scepticism.
Unless this report can provide better numbers than those I am familiar with, it cannot be considered grounds for scepticism.

August 14, 2014 5:07 am

This will have to wait in line to take its turn as yet another neglected variable and feedback (feedback because dry conditions in Asia influence rainfall patterns in the United States, which doubtless affect El Nino and rainfall in the Western Sahara which affect hurricane patterns which probably, eventually, maybe influence drought and wind in Asia again) with no explicit implementation of its spatiotemporal dynamics even at the far-too-large spatiotemporal length scales in the GCMs, behind the errors in cloud dynamics, the projection of the Earth’s orbit onto the dynamically variable albedo and ground/sea structure of the tilted Earth, possible helio-geomagnetic factors, and whether or not the space aliens have their heat ray turned on.

Joel O'Bryan
August 14, 2014 5:27 am

If you up for a laugh, go check out the nutters at:

Joel O’Bryan
August 14, 2014 5:32 am

if you ARE up for a laugh….

August 14, 2014 5:35 am

I would bet this was running in the mountain range north west of Toowoomba Queensland in 2010-11 when the south east corner got flooded http://www.australianrain.com.au/technology/howitworks.html I tried to get john Crook over at SKS to respond seeing that Queensland uni and the BOM were used to take independent readings . Need I say the silence was deafening. The trials in 2008-9 stated that precipitation increased by up to 30% . Here’s some other ionizers in use .http://climateviewer.com/2014/03/26/cloud-ionization-electric-rainmaking-laser-guided-weather-modification/

August 14, 2014 6:25 am

What a refreshing study! No linkage between human caused climate change and increases or decreases in microbes which may cause drought in some areas…but, why do I have this nagging feeling that somewhere on the planet a graduate student is now writing a grant application to prove the linkage?

David in Cal
August 14, 2014 6:56 am

Cloud-seeding has been researched and tried for decades, but it has never worked. Many years ago, statistician John F. said that he got his research funded by telling our military that the Soviet Union was working on cloud-seeding. Today, scientists get funding by claiming that climate change is part of the problem.

Tony Hansen
August 14, 2014 6:59 am

“”We’ve learned that not all of the particles in the air at high altitudes have the same influence on clouds.”
Well fancy that. And I thought the science was settled. Just shows how wrong I can be!

August 14, 2014 7:12 am

“It gets swept westward by the jet stream where it mixes with a variety of other airborne particles such as sea spray and smoke.”
If it is coming to the US, it is going eastward….

Pamela Gray
August 14, 2014 7:57 am

You don’t suppose these researchers took some of their background knowledge about which way the wind blows from Wrong Way Bill Nye? He demonstrates trade winds blowing from the West to the East. You don’t suppose that in one of his other videos he demonstrates the jet stream blowing from the East to the West?
[Now, now, Miss Pam. Latitudes and attitudes rule all. Ole Nye was a clearly southern hemisphere kinda guy, right? .mod]

Pamela Gray
August 14, 2014 7:59 am

An eastern wind comes from the East. An eastWARD wind blows toWARDs the East.

Jim Clarke
August 14, 2014 8:04 am

There does appear to be some real atmospheric science going on here, but let’s not lose sight of the probable magnitude of the impact on weather. Storm systems are generated by atmospheric processes, initially generated by the unequal heating of the Earth’s surface and the Coriolis effect. Mix in a planet that has over 70% of its surface covered in water (most of that liquid) and you will get an abundance of weather, regardless of the pedigree of the various aerosols in the atmosphere.
It is good science to understand how the various kinds of aerosols will effect clouds and precipitation, but that effect is likely to be so small, that knowing the types of aerosols involved would have little to no impact on the weather forecast. I imagine they have to play it up exaggerate, lie) to continue to receive funding.
It is a shame that good science can no longer be funded if it doesn’t involve a significant, immediate social or political impact. Now more than ever, science is a slave to politics.

August 14, 2014 8:12 am

nice snark.

August 14, 2014 8:31 am

Hmmm, bacterial cloud seeding.
I am reminded of one the first environmental releases of transgenic organisms was the “ice-minus” Pseudomonas sprayed onto strawberries to prevent frost damage. That specific proteins can can affect ice nucleation is well known – there is a big business in anti-freeze proteins originally from fish, now produced in yeast, for use in ice-cream manufacture. This provides a different option to chemical based seeding given that proteins degrade in the environment pretty fast.

August 14, 2014 10:43 am

“Microbiologist Dr Chris Van Tulleken examines one of the most radical theories in meteorology today – that some clouds are actually alive, and as a consequence are more likely to form rain than others”

August 14, 2014 7:53 pm

Maybe they should look at the CERN results first, before they get too far into this project.

August 14, 2014 7:56 pm

Biology does produce cloud condensation nuclei. As noted in comments to another post, one explanation for the remarkable warmth of the Cretaceous is lack of clouds due to low productivity of the hot oceans of that Period.

Martin C
August 14, 2014 9:10 pm

rgbatduke says:
August 14, 2014 at 5:07 am
I alway enjoy reading your comments.
Yet this one ( . . in one sentence, no less, . .) is PRICELESS ! ! !

August 15, 2014 2:23 pm

We’ve seen the condensation nuclei bacteria on WUWT before.
Alas, I can’t remember when.
It’s been a couple of years, I think.
Can anyone find it?
It would be interesting to compare these (two or more) posts

michael hart
August 15, 2014 7:08 pm

A general review of (primary) biological aerosol particles in the atmosphere is available free here:

August 19, 2014 10:54 pm

Related – Plankton found outside the ISS:
There’s a lot of new stuff to learn in this age of settled science.

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